Can Anyone Identify This?

I pulled this picture out of the big group photo of Teagues (my father's grandmother's family) and McLaughlins. This is Red McLaughlin as a youth. He is holding a rifle with a very long barrel.

My question is: What era would this rifle have come from? Would it be Civil War era? (Both of Daddy's grandfathers fought in the Civil War.) I'm guessing the photo was taken between 1919 and 1923. His sister, Zudie Lee, was married in 1923, and in the group photo she is without her husband, so I'm guessing she wasn't married yet.

And, just as a random fact, on the Ancestry website there is a feature that tells what a surname means. McLaughlin is an anglecized form of an Irish or Gaelic name that means "Son of the Norseman"--which isn't surprising considering the red hair and blue eyes of my father, and the tall McLaughlin uncles he had. I always figured we got more from the Vikings than from the people who lived in Ireland before the Norsemen came.